JP2771309B2 - Optical reader - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an optical reading device that irradiates a medium on which recorded optical information is displayed with light from a light emitting element and reads reflected light obtained by a light receiving unit. More particularly, the present invention relates to an optical reading device in which irradiation light is improved in order to improve reading accuracy.

[Conventional technology]

The optical reading device illuminates a bar code or the like as an example of a display optically recorded on the surface of a medium, and detects the obtained reflected light by a light receiving unit. The light receiving means includes, for example, a line sensor or the like in which a plurality of light receiving elements are arranged, and a light receiving lens or the like which is a reduction optical system. Then, the information recorded on the medium is converted into an output signal that can be subjected to calculation processing by an electronic computer by subjecting the electric signal sequentially obtained from the light receiving element to waveform processing such as binarization.

Such a conventional optical reader will be described with reference to FIGS. 13 and 14. FIG. FIG. 13 is a layout diagram showing an outline of an optical system configured in the optical reading device, and FIGS.
FIG. 4 is a waveform chart for explaining the operation of the figure.

From a light source 21, which is a light emitting element having a plurality of LEDs, a medium 22 in which bars and spaces are optically displayed in a predetermined range.
Are illuminated as shown by five arrows parallel to FIG. The reflected light scattered from the surface of the medium 22 reaches the line sensor 23 via the lens 25 of the reduction optical system.

When the light source 21 of such an optical reader illuminates the medium 22 in a range in which the line sensor 23 can receive light with a uniform illuminance distribution, and when the surface reflectance of the medium 22 is constant,
As shown in FIG. 3B, the line sensor 23 receives light when the amount of light reflected from the medium 22 at both ends illuminated gradually becomes lower than the amount of light reflected at the illuminated central portion. Therefore, in order to equalize the amount of reflected light at the center portion and at the end of the range received by the line sensor 23, as shown in FIG. With respect to the illuminance at the central portion of the illuminator, the illuminance gradually increases as the illuminance moves toward both ends. This illuminance distribution is, for example,
As described in -17270, the LED arrangement interval or each LE
This is achieved by changing the value of the current flowing through D. Accordingly, when the surface reflectance of the medium 22 is constant, the amount of reflected light from the illuminated medium 22 becomes uniform within the illuminated and receivable range as shown in FIG. Is received at.

When a barcode is displayed in the range where light is received by the line sensor 23, the result is as shown in FIG. 14 (d).
First, a space called a start margin or a stop margin is provided on both sides of the barcode. This is to improve the security of reading, and the barcode standard specifies a width larger than the width of a bar or space of an effective data portion. Usually, the read signal is taken out from either side of the bar code, so that a signal corresponding to white is initially output. Next, when the first bar of valid data is detected, a large rising amplitude waveform indicated by the symbol “E” in the figure appears at the output of the line sensor 23, and subsequently, the bar code display is continuously detected. Then, a repetitive amplitude waveform indicated by a symbol “e” in the same drawing appears in the output of the line sensor 23 corresponding to the repetition interval between the bar and the space. Here, the reason why the amplitude “e” after the initial rise is smaller than the amplitude “E” at the first rise is that in the case of this type of reader, usually, the fineness of the barcode to be read is It is not designed with a highly accurate optical system or a high-resolution light-receiving element (due to cost).
So unless you are reading a particularly coarse barcode,
The boundary between the bar and the space "dissolves" due to the performance of the optical system and the light receiving element. As a result, the output from the light receiving element has a waveform as if a low-pass filter has been applied, that is, a waveform in which the amplitude of a small portion is reduced. Such an analog signal output waveform of the line sensor 23 is supplied to a computer via a waveform processing circuit (not shown) and is subjected to calculation processing.

[Problems to be solved by the invention]

However, in the conventional optical reading device, the display start and end positions of the barcode or the like to be read come near the end of the range readable by the line sensor 23, and FIG. When the light is illuminated with the illuminance distribution indicated by, the analog signal output waveform of the line sensor 23 between the display start and end positions (the start position in the case of barcode display and the position where the stop bar is located) is The amplitude of the analog signal output waveform of the line sensor 23 at the time of detection of the bar code display is large, and it is difficult to perform accurate waveform processing in the waveform processing circuit due to a large amplitude. Have.

Accordingly, the present invention provides an optical reading device that can obtain an averaged reflected light amount in a range readable by the line sensor 23 and obtain an output signal that can be easily shaped and that can be accurately calculated. Is a technical issue.

[Means for solving the problem]

In order to solve the above-described problems, the present invention provides a light receiving unit for detecting a medium to be read with a predetermined width, a light emitting unit for supplying light to the medium at a position where the light receiving unit reads, and a light emitting unit. A light guide means thin at a predetermined illuminance distribution to the position of the medium read by the light receiving means the light emitted, and, the illuminance distribution on the medium from the light guide means,
For the illuminance at the center of the range read by the light receiving means,
The configuration is such that the illuminance at the middle position between both ends and the center of the reading range is set high.

[Action]

 The above technical means works as follows.

That is, the illuminance at the end of the range readable by the line sensor, which detects the boundary between the non-display surface of the medium and the display start and end positions, is relatively higher than that at the center of the range readable by the line sensor. Since the illuminance is configured to be lower than the illuminance near the center of the end of the range readable by the illuminated line sensor, the boundary between the non-display surface and the display start and end positions is detected, Since the difference between the amplitudes of the analog signal output waveforms of the line sensor and the case where the end position is detected is small, the subsequent waveform processing is easy and accurate, and the reading success probability is improved.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS. 1 to 12. The detailed description of the same and same functional portions as those described in the conventional example is omitted.

1 (a) to 1 (c) are waveform diagrams for explaining the operation of the optical reader according to the present invention, and FIG. 2 is a cross-sectional view of a main part of an illuminating section of the optical reader according to the first embodiment of the present invention. Figure, FIG. 3 (a)
2 (b) is a waveform diagram showing the illumination characteristics of FIG. 2, FIG. 4 is a cross-sectional view of a main part of an illumination section of an optical reader showing a second embodiment of the present invention, and FIG. FIGS. 6 (a) to 6 (c) are waveform diagrams showing the illumination characteristics of FIG. 4, FIG. 7 is a waveform diagram for explaining the illuminance distribution on the medium surface, and FIG. 9 (a) and 9 (b) are waveform diagrams showing the analog output of the line sensor, FIG. 10 is a waveform diagram for explaining the operation of the signal processing circuit, FIG. 11 is a waveform diagram showing the polarity of a signal supplied to an AC amplifier circuit of the optical reader, and FIG. 12 is a configuration diagram showing a circuit of the optical reader.

In the figure, 1 is a medium, 2 is a barcode, 4 is a light source, 3a
Is an LED, 3b is a lens as a light guide means, 3c1 to 3c3 are lens parts, 4 is a light receiving lens, 5 is a line sensor, 6 is a DC amplifier circuit, 7 is an AC amplifier circuit, 8 is a binarization circuit, 9 is a decoder, 10 is a constant voltage circuit, 11 is a frequency divider circuit, 12 is a clock circuit, 13 is a power supply circuit, and 14 is a drive circuit.

First, the overall configuration of the optical reader will be described with reference to FIG. The reflected light from the surface of the medium 1 on which the bar code 2 is displayed passes through a lens 4 which is a reduction optical system in a line sensor 5 in which a plurality of light receiving elements 2 of CMOS type or CCD type are arranged in a row. It can receive light. A reading start signal output from a host device (not shown) based on an operation of a push button or the like (not shown) by an operator is a power supply circuit.
The light source 3 is driven to emit light with a constant current for a predetermined period by the driving circuit 14 supplied with power from the power supply circuit 13, and the clock circuit 12 supplied with power from the power supply circuit 13 starts counting from an initial value. Decoder 9 powered by
Are set to a state where the decoding operation can be started.

From the constant voltage circuit 10 supplied with power from the power supply circuit 13, the charging voltage of the line sensor 5, the amplification operation voltage of the DC amplification circuit 6, the amplification operation voltage of the AC amplification circuit 7, and the And a binarized operating voltage, which is stabilized and applied constantly.

The frequency dividing circuit 11 supplied with power from the power supply circuit 13 has a reading period corresponding to the number of light receiving elements (phototransistors) of the line sensor 5 and a repetition cycle of the clock pulse from the clock circuit 12, and a light amount exposed by the reflected light. The clock pulse supplied from the clock circuit 12 is frequency-divided and a detection command signal is supplied to the line sensor 5 so as to indicate a charging period for changing the clock signal into a voltage signal. The line sensor 5, to which both the detection command signal and the clock pulse are supplied, supplies a pulse indicating the charging period of the detection command signal to the charging elements (semiconductor capacitors) connected to the respective light receiving elements at the same time. As soon as the currently charged electric charge is instantaneously reset to the initial value, the charging voltage is applied to all the light receiving elements for a period corresponding to the time during which the pulse is supplied. The line sensor 5 in this state does not depend on the supplied clock pulse.
A charging current corresponding to the amount of light received by each light receiving element is supplied to each charging element connected to each light receiving element. Then, the line sensor 5 to which the detection command signal indicating the readout period is supplied, changes the voltage value corresponding to the amount of electric charge supplied to each charging element 2 in the scanning cycle corresponding to the period of the supplied clock pulse. The output is sequentially made to the DC amplifier circuit 6.

The weak analog waveform signal sequentially read from the line sensor 5 is amplified to a predetermined power by the DC amplifier circuit 6, and is sequentially supplied to the AC amplifier circuit 7 via the DC coupling AC coupling capacitor. . The AC amplifier circuit 7 supplies an amplified signal corresponding to the AC component of the analog waveform signal output from the line sensor 5 to the binarization circuit 8. The binarization circuit 8 clamps the upper and lower leading values of the amplification value of the AC component whose analog waveform signal is amplified in accordance with the level of the surface reflectance of the medium 1 received by the line sensor 5 by a well-known waveform shaping means. Then, the clamped AC signal is binarized with a fixed threshold voltage, and the binarized signal of “H” and “L” level is output to the decoder 9. The decoder 9 converts the binary signal to "H" and "L" based on the clock pulse supplied from the clock circuit 12.
The continuous time of the level is measured, the image data is sequentially decoded and converted into character data based on the measured value, and the decoding result is output to the host device.

The light source 3 having an LED array in which a plurality of LEDs are arranged includes:
The range W of the medium 1 that can be detected by the line sensor 5 is illuminated with an illuminance distribution as shown in FIG. This illuminance distribution is similar to the conventional illuminance distribution described with reference to FIG. 14 (a) in that the central portion of the range W is lower than the illuminance on both sides thereof, but FIG. As shown by the symbol “X ₀ ” shown in a), a position close to the center by a small distance X ₀ from the end of the range W is set to be the highest illuminance, and the illuminance at the end of the range W is than the illuminance of the position of the distance X ₀ is set lower. The distribution of the received illuminance of the line sensor 5 that has detected the reflected light from the medium 1 illuminated with this illuminance distribution is as follows.
When the reflectance is constant, the illuminance gradually decreases toward the end of the detection area w of the line sensor 5 shown in FIG. 12 as shown in FIG. 1B. This light receiving illuminance distribution state is different from the conventional light receiving illuminance distribution described with reference to FIG. 14 (b) in that the light receiving illuminance distribution at the center of the detection area w is flat. The illuminance at the end of the detection area w is set to gradually decrease unlike the conventional distribution of the received illuminance described with reference to (c).
Therefore, an analog signal waveform output from the line sensor 5 which detects a non-display area having a high average reflectance and a boundary of the display area of the bar code 2 from a display start position to an end position having a lower average reflectance. Is different from the waveform described with reference to FIG. 14 (d), in that the amplitude amount E when the display start and end positions are detected from the non-display area as shown in FIG. And a difference between the amplitude width e and the amplitude width at the time of detection from the display end position is small.

Next, the reading operation of the optical reading apparatus thus configured will be specifically described with reference to FIGS.

The waveform diagram shown in FIG. 7 is for explaining the relationship between the illuminance distribution of the medium 1 and the display position, and is used in the optical reading apparatus of the present invention described with reference to FIG. The illuminance distribution curve when the medium 1 is illuminated is shown by a solid line, and the illuminance distribution curve when the medium 1 is illuminated by the conventional optical reader described with reference to FIG. I have.

The range of the surface of the medium 1 that can be detected by the line sensor 5 is:
In the range of code "X _E" from the code "O" in the horizontal axis direction X shown in FIG. 7. Illuminance distribution curve of this example, as shown by the solid line in bimodal in Figure 7, inside the detectable range O～X _E on the surface of the medium 1, detectable limit position O at both ends, in the vicinity of the X _E, maximum illuminance position P ₁ of the pair showing a maximum illumination intensity value I _p1 is generated. Distance X ₀ of the case where the distance between the line sensor 5 and the medium 1 are opposed by the standard distance, the limit position O and a maximum illuminance position P ₁ reading one is longitudinal normally 15 mm. Limit position O of the pair of maximum illuminance position P ₁ and the opposite ends, the display end position is a display start and end positions of the medium 1 showing the lower illuminance value I _S than the maximum intensity value I _p1 between X _E It is assumed that B _S will come. The display end position B _S when the display of the medium 1 is a bar code, displayed during bar display end position of the display start position is start bit is a bar of Sutotsupu-bit indicates the data content or the like Spaces and bars are arranged. Then, the optical reading apparatus, the detectable range O～X _E
In this case, the entire content of the display is detected when the display is faced so that the area from the start to the end of the display fits within the width W of. At this time, when the display range is positioned such that the interval _S from the display end position B _S to the limit position O is shorter than or equal to the interval X ₀ between the maximum illuminance position P ₁ and the limit position O. Improves the reading probability.

The detection range w of the line sensor 5 detects the range of the reading angle θ centered on the lens 4 which is disposed at the lens position shown in FIG. This reading angle θ
Since the distance b between the line sensor 5 and the lens 4 is kept constant, it can be read in a certain angle range. Here, the relationship between the first detection position where the reflected light from the surface of the medium 1 forms an image on the light receiving surface of the line sensor 5, the reference distance a to the lens 4, and the distance b between the line sensor 5 and the lens 4 When 4 is the reduction magnification m, it becomes as shown in the first expression.

m = b / a Expression 1 The reduction magnification m of this lens is set to a value such that the optical reading device can be held by one hand based on the detection width w of the line sensor 5, for example, about 0.25. The readable range W of the optical reading device at the first detection position, which is the reference position where the medium 1 is to be disposed, has a width represented by the second expression that is directly proportional to the distance a with respect to the constant of the reading angle θ. .

W = 2 · a · tan (θ / 2)... Second formula The reading is possible at a second detection position that is further away from this distance a by a limit distance d that can be detected even if a defocus is detected by the line sensor 5. The range W 'is a width represented by the third expression that is directly proportional to the sum of the distance a and the distance d with respect to the constant of the reading angle θ.

W ′ = 2 (a + b) · tan (θ / 2) Equation 3 The display end position Bs ′ of the medium 1 that faces when the readable range W ′ at the second detection position separated by this distance d is W ′. 'spacing S to' the readable limit position when 0, than the distance Xo 'to the' readable limit position as when the 0 'maximum illumination intensity location P ₁ of the time, the shorter or the same In this way, good detection and decoding results can be obtained by arranging them in opposition.

When the bar code 2 displayed on the medium 1 is read by the optical reading device, the signal waveform supplied to the AC amplifier circuit 7 via the AC coupling capacitor has a white level of the display as shown in FIG. At a high voltage, the displayed black level is output with a low voltage polarity. This signal waveform is different from the average change rate of the average level curve shown by the broken line in FIG. 9 (a) obtained when illuminated by the illumination characteristic of the illumination distribution curve shown by the broken line in FIG. The average change rate of the average level curve shown by the broken line in FIG. 9B obtained when the light is illuminated with the illumination characteristics of the bimodal illumination distribution curve shown by the solid line in FIG. 7 is small. This difference in the average change rate is caused by the magnitude of the illuminance illuminated at the boundary between the display and the non-display area, and the voltage changes V ₁ and V ₂ occurring at the boundary between the non-display area and the display area are large and small. It depends directly on things. That is, Dengo change V ₂ that occurs when the boundary between the non-display area and the display area as in the present invention are illuminated at a relatively low illuminance, the boundary between the non-display area and the display area is illuminated with a high intensity quite small value and Narutsu the voltage change V ₁ occurring when you are.

The magnitude of the voltage changes V ₁ and V ₂ generated at the boundary between the non-display area and the display area depends on the waveform output from the AC amplifier circuit 7 as shown in FIG. 10 when the same medium is detected at the same distance. When a certain threshold voltage _Vth is passed from the value at which the change direction of the threshold value changes, an error occurs in the result of the determination operation in the binarization circuit 8 that changes the output value. That is, the width W ₂ of the binarization output waveform shown in FIG. 10 the solid line rectangular voltage change V ₁ which varies greatly is obtained is determined by the fixed threshold voltage V _th is a voltage of less change change V ₂ There time interval with respect to the width W ₁ of the binarization output waveform shown by a broken line rectangle in Figure 10 obtained is determined with the same threshold voltage V _th is long Narutsu. This is shown in FIG. 9 (a)
And (b) as well as in FIG. 10, but are displayed in response to the reading start side shown at the limit position 0 in FIG. 7, similar results are obtained for reading end side of the limit position X _E. Therefore,
The decoder 9 is a signal supplied from the binarization circuit 8, for the case of decrypting a wide binarized output waveform of the width W _2, when to decode the binary output waveform having a width W ₂ than the width W ₁ Is significantly less likely to produce a decoding error.

The light source 3 of the optical reader having the improved decoding probability.
As an example, as shown in FIG. 4, the X direction shown on the surface of the wiring board 3d (that is, the reading direction of the line sensor 5;
(See Fig. 12)
a, 3a ... are arranged. This interval is such that the central portion of the wiring board 3d with respect to the central portion of the reading range W of the line sensor 5 is coarse, and is densely arranged toward the end of the wiring substrate 3d. The cross-sectional shape of the plurality of LEDs 3a, 3a,.
The reading direction of the line sensor 5 and the parallel direction do not change the same,
A light guide 3b for condensing light having a semi-cylindrical shape in which a distance direction between the line sensor 5 and the medium 1 is substantially a radius is arranged.

The illuminance distribution of the light source 3 formed in this manner is similar to the characteristic indicated by the solid line in FIGS. 1A and 7 for the medium 1 opposed to the optical reader at a standard interval. Fig. 6 shows a bimodal distribution curve shown in Fig. 6 (a). As shown in FIG. 5, the illuminance distribution for one LED 3a is symmetrical in the left and right directions and has a shape in which the central portion has the highest illuminance. Therefore, when the distance between the medium 1 and the LED 3a is changed, the illuminance distribution when the distance is short is such that the illuminance in the central portion is high and the distribution characteristics deviate from the center, and the illuminance distribution sharply decreases. As the distance increases, the illuminance distribution changes to a mountain-like shape in which the illuminance in the center decreases and the illuminance changes gradually as the distribution characteristics deviate from the center. And change.

Therefore, the change characteristic of the distance illuminance distribution of the light source 3 composed of a plurality of LEDs 3a, 3a,... When the distance is close, a bimodal distribution curve is shown as shown in FIG. 6 (a), and as the distance gradually increases, the central part is flattened as shown in FIG. 6 (b). Shows a distribution curve that is lower from both ends to Nada.
As shown in FIG. 3C, a distribution curve in which the illuminance gradually decreases from the center to both ends is shown. As described above, in the optical reading device in which the illuminance distribution curve changes with the distance, as the distance between the medium 1 and the line sensor 5 gradually increases, the received illuminance of the reflected light illuminated by the line sensor 5 increases the detection range. Higher at the center than at the end of w. Therefore,
When the distance between the medium 1 and the line sensor 5 is large, decoding errors in the decoder 9 occur frequently.

A plurality of LEDs 3a, 3a... Are arranged at equal intervals with respect to the above light source, and a light guide 3b for light collection having a similar semi-cylindrical column shape faces the row of the LEDs 3a, 3a. When the LEDs are arranged, the same operation is performed even if the drive current values of the LEDs 3a, 3a,...

On the other hand, in order to maintain the reading probability in a predetermined range even if the distance between the medium 1 and the line sensor 5 is large, the light source 3 as shown in FIG. ; See FIG. 12), a light guide 3b taking into account the light-collecting characteristics is used. In the light guide 3b shown in FIG. 2 having different light collecting characteristics, a plurality of lens portions 3 _C1 , 3 _C2 and 3 _C3 forming a Fresnel lens are different from the light guide 3b shown in FIG. The formed light guide 3b is arranged to face the plurality of LEDs 3a, 3a,.... Each of the LEDs 3a, 3a,..., Which are arranged at a finer interval toward the end of the light guide 3b so as to be supplied with the same drive current, is arranged in the light guide 3b. each lens unit 3 _C1 to 3 _C3 at intervals corresponding are arranged corresponding to the pitch. Refraction angle of the lens unit 3 _C1 and the lens unit 3 _C2 disposed in the vicinity of the end portion of the light source 3, whereas in its central portion at an angle larger than the lens unit 3 _C3 positioned at the center of the light source 3 toward Once refracted.

And this light source 3 constituting the Fresnel lens is
When the optical reader and the medium 1 are arranged facing each other at a standard interval, a bimodal illuminance distribution as shown in FIG. 3A is obtained. Therefore, when the line sensor 5 and the medium 1 shown in FIG. 8 are opposed to each other at a distance d from the reference distance a, the illuminating range is widened as shown in FIG. Is low overall,
The bimodal illuminance distribution is maintained.

The boundary between the non-display portion and the display portion of the medium 1 in which the distance from the display start position to the display end position is widened is the end of the readable range W in a state where the distance between the line sensor 5 and the medium 1 is large. A relatively large number of them are arranged to face each other in the vicinity. Therefore, the vicinity of the boundary where the width is displayed is detected while being illuminated by the bimodal illumination distribution even when the optical reading device is arranged to face away from the optical reading device. The result is obtained.

In the embodiments described so far, the light receiving means has been described as the line sensor 5 in which the reduction lens 4 is disposed on the front surface. However, the present invention is not limited to this, and the light receiving means may be provided from the non-display area of the medium 1. As long as the display area is illuminated with the illumination distribution characteristics according to the present invention and the resulting received values are processed in the order in which the display contents should be decoded, the light receiving means may be of another type. For example, a predetermined width on the medium may be read by combining a single light receiving element and a scanning mechanism such as a galvanometer mirror instead of the line sensor. Alternatively, the same effect can be obtained by a method in which a plurality of light receiving elements are read out in a predetermined order from a light receiving solid state device arranged in multiple rows.

Further, the light source of the above-described embodiment has been described with the configuration of illuminating the medium at the same time.

〔The invention's effect〕

As described above, the optical reading apparatus of the present invention sets the illuminance at the end of the display area having a low average reflectance higher or equal to the illuminance of the non-display area having a higher average reflectance. When the boundary between the display area and the display area is detected, the level fluctuation of the detection signal generated at this boundary is reduced, so that a complicated processing circuit for avoiding the influence of the level fluctuation at this boundary is not required, and a simple operation is possible. Since the signal decoding operation can be stably performed by the circuit configuration, the rate of occurrence of decoding errors is reduced, so that an optical reading device which can be easily handled can be provided.

[Brief description of the drawings]

1 (a) to 1 (c) are waveform diagrams for explaining the operation of the optical reader according to the present invention, and FIG. 2 is a cross-sectional view of a main part of an illuminating section of the optical reader according to the first embodiment of the present invention. FIGS. 3 (a) and 3 (b) are waveform diagrams showing the illumination characteristics of FIG. 2, and FIG. 4 is a cross-sectional view of a main part of an illumination section of an optical reader according to a second embodiment of the present invention. Fig. 5 is a waveform diagram for explaining the illuminance distribution of the LED,
6 (a) to 6 (c) are waveform diagrams showing the illumination characteristics of FIG. 4, FIG. 7 is a waveform diagram for explaining the illuminance distribution on the medium surface, and FIG. 8 is an outline of the optical system of the light receiving means. 9 (a) and 9 (b) are waveform diagrams showing the analog output of the line sensor, FIG. 10 is a waveform diagram for explaining the operation of the signal processing circuit, and FIG. 11 is an optical reader. FIG. 12 is a waveform diagram showing the polarity of the signal supplied to the AC amplifier circuit shown in FIG. 12, and FIG. 12 is a configuration diagram showing the circuit of the optical reading apparatus, and FIG. 13 and FIG.
(D) is a diagram for explaining a conventional technique. In the figure, 1 is a medium, 2 is a barcode, 3 is a light source, and 3a is
LED, 3b is a lens as light guiding means, 3c1 to 3c3 are lens parts, 4 is a light receiving lens, 5 is a line sensor, 6 is a DC amplifier circuit, 7 is an AC amplifier circuit, 8 is a binarization circuit, 9 Denotes a decoder, 10 denotes a constant voltage circuit, 11 denotes a frequency divider circuit, 12 clock circuits, 13 denotes a power supply circuit, and 14 denotes a drive circuit.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-138681 (JP, A) JP-A-64-12384 (JP, A) JP-A-61-54570 (JP, A) JP-A 64-64 3819 (JP, A) JP-A-62-166478 (JP, A) JP-A-61-190673 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G06K 7/10

Claims (3)

(57) [Claims] 1. A light receiving means for detecting a medium to be read with a predetermined width, a light emitting means for supplying light to the medium at a position read by the light receiving means, and a light receiving means for receiving light emitted by the light emitting means. Light guiding means for guiding a predetermined illuminance distribution to the position of the medium to be read, and the illuminance distribution on the medium from the light guiding means is set to the illuminance at the center of the range read by the light receiving means. for,
An optical reading device wherein the illuminance at a position between both ends and a center of a reading range is set high. 2. The optical reading device according to claim 1, wherein the light emitting means includes a plurality of light emitting elements arranged at predetermined positions, and the plurality of light emitting elements illuminate the medium with the illuminance distribution. The optical reading device is arranged at predetermined positions at unequal intervals so that the plurality of light emitting elements are turned on at the same time. 3. The optical reading device according to claim 1, wherein the light emitting unit includes a plurality of light emitting elements arranged along a reading direction of the light receiving unit, and the light guiding unit includes the plurality of light emitting elements. An optical reading device having a curved surface that is bent toward the outer side as the optical axis of the light emitting element disposed outside the light receiving unit in the reading direction with respect to the light receiving unit.